This application relates generally to steering columns and more particularly to a responsive energy absorbing device for a steering column.
Many steering column assemblies today are equipped with kinetic energy absorption devices to reduce the likelihood of injury in case of an accident. Such devices come in many different forms. One form that is particularly effective in absorbing significant quantities of energy in a relatively small amount of space employs a plastically deformable member such as a metal strap which is bent over an anvil. In the event of a head-on collision, the deformable strap is drawn across the anvil and the deformed shape travels along the length of the strap, causing a reaction force resisting collapse of the steering column and absorbing energy.
Typically energy absorbing devices, such as those employing a plastically deformable strap, are designed to protect drivers of average weight in a collision of average severity, without taking into account the fact that all drivers are not of average weight and that collisions vary considerably in severity depending on vehicle speed at the time of the impact.
In accordance with the present invention, it is possible to vary the reaction force resisting collapse of the steering column. For example, the energy absorbing device of this invention may provide a smaller amount of resistance in the case of a less severe collision or a lower weight driver, or a greater amount of resistance in the case of a more severe collision or a driver of greater weight.
The resistance is preferably provided by a plastically deformable strap supported on one side at spaced points. An anvil displaces a portion of the strap between the points of support into a V-shape to increase the energy required to advance the strap and thereby increase the resistance of the strap to the collapse of the steering column. The position of the anvil may be varied to vary the amount of displacement of the strap, or the anvil may be removed altogether depending upon conditions detected by a controller either before or at the instant of the collision.
In one form of the invention, several anvils may be provided to form the strap into two or more V-shaped wave formations with one of the anvils of at least one such formation in the form of a releasably supported pin. The releasably supported pin may be dropped out of the system in instances where less resistance to collapse is desired.
Further in accordance with the invention, one of the anvils may be supported in one position in which a section of the strap is displaced into a deep V-shaped configuration, or in another position in which the section of the strap assumes a shallow V-shape.
The resistance force of the deformable member is varied in proportion to the severity of the collision, or the occupant""s weight, etc. Using measurements of the crash conditions, this invention relocates one or more of the V-shape forming anvils to vary the resistance force on the driver and this may be accomplished by an actuator. The actuator is actuated in only a few milliseconds preferably by a pyrotechnic device or electronic solenoid, which is responsive to a signal from a controller that measures the pertinent conditions existing at the time of the crash.
This invention extends the range of effective injury reduction of an energy absorbing steering column by increasing or decreasing the reaction force available during the displacement of the steering column in response to driver weight and vehicle speed measurements before or during the crash event.
One object of this invention is to provide an energy absorbing device having the foregoing features and capabilities.